Remote indicating and control system



Sep@ E29 MEQ@ E. G. WATTS REMOTE INDICATING ANDCONTROL SYSTEM Filed Nov.27, 1934 s' sheets-sheet 1 www.

INVENTOR.

A RNEY5 E., G. WAT-rs. 2,172,918 REMOTE INDICAJIINCa| A-ND CONTROLSYSTEM!l Filed Nov. 27,- 1934 3 Sheets-Sheet 2 Kimm.

.ummm-ammi( INVENTOR.

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sept. i2, w39. E. G. WATTS l 2,172,918- REMOTE -INDICATING AND CONTROLSYSTEM Filed Nov. 27', 1934 3 lSheets-Sheet 5 20 must be located at thetransmitter.

Patented Sept. 12, 1939 l f UNITED. STATES PATENT ori-ics minorsINDICATTNG AND comon v SYSTEM Application November 27, 1934, Serial No.'155,047t 1s claims. (Cl. 177451) This invention relates to a system forelectrically indicating, recording, or controlling at a remote pointvariations of a quantityor magnitilde, such as fluid pressures, liquidlevels, energy,

5 rate of ow and-the like. More particularly, the

invention relates to the measurement or recording of iiuid pressures orows at a point remote from the pressure point to be measured.

Telemetering systems have heretofore been proposed in which there is anoscillatory electrical circuit at the transmitter with means such as areactance actuated by the value to be measured for varying the frequencyof the oscillations of the circuit, and the changes in the frequency ofthe oscillatory potential are transmitted and impressed cn a suitableindicating instrument at the receiver. To my knowledge such systems asheretofore constructed have the disadvantage that the source ofelectrical energy for the transmitter Also, as the transmission line hasa certain .capacity any changes therein due to various uncontrolledcauses will affect the frequency of the transmitter. Where the pressureor rate of. ow of in- 25-ammable uids are to be measured such systemscannot be employed because of the fire hazard attendant on the use ofhigh voltage currents of commercial power transmission lines. Also, itfrequently happens that poweris not available at the transmitter for itsoperation because of the isolated location of the transmitter.

Further, to my knowledge, prior systems of this type have had a limitedmeasuring range due to the fact that the variable reactance at the y, 35transmitter must be made too large and cumbersome to be operativeforindicating practical ranges. with the consequence that when a wide rangeof indication or extreme accuracy in reading is desired this reactanceelement must be 40 made so large and heavy that the system loses itssensitivity and becomes unreliable as an inj dication of small changesin the value to be measured. If the size of the reactance element is notincreased it is not possible to obtain a suffi- 45 ciently wide range ofoperation'topermit accurate reading of the scale on the indicatinginstrument rent from interfering with the receiver, and isob5 late thesignalling current from the power sup- Dly. By this arrangement I amenabled to have the power supply for the transmitter located at thereceiver, the power being conducted thereto over the same conductorswhich carry the oscillating signal potential from the transmitter to 6the receiver. Or, in a modification, a power supply is located at anintermediate point between the transmitter and receiver and furnishespower to the transmitter, the oscillating signal potential beingreturned over the same conductors as 10 far as the power, supply andthence to the receiver. Instead of recalibrating the receiver to permitits use in this modification I shunt a resistance across the powersupply terminals of the receiver equal to the transmission lineresistance and resistance of the transmitter. In a third modificationthe power supply for the transmitter is located adjacent thereto, thesignalling potential beingisolated therefrom as before, and the powersupply likewise being isolated from the receiver.

In employing a vacuum tube osciliatorat the transmitter I provide meansfor vdividing the supply potential, utilizing a portion thereof in theplate-filament circuit, said means being in the path of thegrid-filament oscillating current for producing an alternating potentialdiiference, and\I tap the signalling potential across said means. Thedirect current potential of the grid is adjustable for various circuitcharacteristics,

vand I provide a low reactance path in the oscillating grid-lamentcircuit which prevents iiow of direct current therethrough but permitsflow of the oscillating grid-filament current. I also provide means forcompensating for the eifect of the transmission line on the transmitter.

Further, I provide a transmitter comprising an oscillatory circuit andareactance such as a condenser or an inductance actuated by the value tobe measured for varying the frequency of the 40 circuit, and I insert insaid oscillatory circuit a means multiplying the reactance effect of thefrequency'varying means whereby, without increasingthe size or weight ofthe frequency varying means or diminishing -the accuracy thereof, themeasuring range of the transmitter is increased. This transmitter can beemployed in connection with the vacuumv tube osciilatorjust described.The modification in which the power supply is 4located at the receiverand is common to the 50 receiver and,transmitter,when'used in connectionwith my improved oscillatory circuit above described, can beemployed upto ranges of about ten miles over commercial telephone lines. Forfurther rangesI prefer to locate the vpower sup-I ply for thetransmitter any convenient distance therefrom up to about ten miles, andthe receiver may be located one hundred miles or more-from thetransmitter. These ranges are increased. as for example, by usingspecial wiring in place of commercial telephone lines or by usingsuitable amplifying devices at suitable points between the transmitterand receiver. The amplifier is coupled to the receiver in such mannerthat the amplifierK requires a minimum signal potential to provide ytherequired power for operating the receiver.

In the specific embodiment in which a condenser is used to vary thefrequency of the oscillatory circuit including a thermionic valve at thetransmitter, I inductively couple the secondary oscillatory circuit tothe primary oscillatory the secondary oscillatory circuit and thusincrease the measuring range of the transmitter without increasing thesize of the condenser which is actuated by the value to be measuredwhile retaining its accuracy and sensitivity. A commonv path is providedfor the plate-filament and grid-filament oscillating currents, andthesignalling potential is taken at the terminals of this path.

Accordingly, it is one object of the present trol system employing anoscillatory circuit at the transmitter which receives its source ofelectrical energy from a point remote therefrom.

, Another object is to provide a telemetering system in which the poweris conducted to the transmitter over the'same wires that conduct thesignalling potential to the receiver, the power current and signallingcurrents being isolated.

Another object is to provide means for compensating for the etl'ect ofthe transmission line on the transmitter.-

` A further object is the provision'of a transmitter of' the oscillatorytype in which the meas-- uring range is increased without loss ofsensitivity of the instrument and without destroying its accuracy.

Another object is the provision of an amplifier at the receiver, theoutput thereof being coupled to the receiver so that the amplier willdevelop the required power for operating the receiver with a minimumsignal potential.

I Another object is the provision of an oscillator of the vacuumtubetype employing a novel arrangement for supply current .and fortapping the oscillating signalling current.

Another object is the provision of a receiver including a frequencymeter andhaving means for checking the accuracy thereof at apredetermined frequency.

These .and various other objects of the invention will be apparent fromthe following description and Aappended claims taken in connection withthe accompanying drawings in which: Figure 1 is a wiring diagram of areceiver having the power supply contiguous thereto:

' s Figure 2 is a wiring diagram of a preferred embodiment of thetransmitter;

Figure 3 is awiring diagram in which the power supply for thetransmitter is located ,at some in- 7'0 termediate .point between thetransmitter and receiver;

Figure 4 -is a wiring diagram of a modified transmitter;

. Figure 5 shows a modified transmitter for pro- 75 -ducing a variablefrequency potential;

circuit thereby dividing the reactance eifect of invention to provide atelemetric or remote con- Figure 6 is a wiring diagram of a modifiedtransmitter employing a variable inductance;

Figure 7 is a wiring diagram of a modified transmitter, the signallingpotential being tapped in the grid-filament circuit; 5

Figure 8 is a wiring diagram of a modified transmitter, the signallingpotential being tapped in the plate-filament circuit;

Figure 9 is a wiring diagram of a modification showing a three wiresystem, the power supply 10 and signal potential being segregated at thetransmitter.

Referring to the drawings, the modification shown in Figures 1 and 2comprises a transmitter -A, a receiver B, and a power supply C, thelatter being located at the receiving end of the system. Thismodification is particularly useful when the transmitter is located atsome remote section in which a source of high potential electrical poweris not available, or in oil elds where high potential lines are notpermitted, and the arrangement is such that 'direct current istransmitted to the transmitter over the same telephone lines whichreturn the alternating current signal of the transmitter to thereceiver. 25

The power supply 'Ihe power supply receives a regulated alternatingcurrent from any suitable source through `.a voltage regulator 2 whichis converted into 30 the modiilcation shown a secondary winding 4 ofthis transformer is connected to the cathode or lament of `the vacuumtube rectifier 1 for 35 heating the same, and the secondary winding 5 isconnected at its terminals to the anodes or plates thereof. Thesecondary windings 4 and i are tapped at their respective centers 6 and8 and these taps constitute the positive and nega- 40 tive outputterminals respectively of the rectifier. The positive terminal 6 isAconnected to one terminal of capacitor 3 and the negative terminal '8is connected to one end of inductor or reactance 9, the oppositeterminal of reactance 9 being 45 connected to the other terminal ofcapacitor 3. The capacitor or condenser l and the reactance 9 provide asmoothing action to the current supplied by the rectifier to the pointVwhere it is desired to apply the direct current. Further smoothing ofthe direct current is provided by the capacitor I0 and a reactance IIwhich repeats this process to insure maximum smoothing action, or, inthis case, provide a pure non-pulsating direct current available lforapplication from ,the points I2 and I4 to the transmitter A, to thereceiver B, `and to the amplifier when used.A A safety fuse I1 isinserted on the output vside of the rectier tube.

'I'he receiver terminals I3 and Il are connect- ,o ed to the transmitterterminals Il' and I5' respectively by the two wires of a telephone line,the terminals I8 and 'ISi being grounded by a wire I8' to the metal caseof the receiver as indicated at I8. The direct current isftrans- 55mitted over the telephonelines to the positive terminal I3 and negativeterminal I5' at the transmitter A.- (Figure 2.) The potential of thepositive .transmitter terminal Il' of the telephone liney is adjusted tothe proper value by means of a variable resistance 20 in series with aiixed resistance Il, an inductance Il and an ammeter 2|, the meter' 2|being used to provide a visible indication'of the current so thatresistance 20 can be manually adjusted to pro- 75 direct currentsupplied tothe transmitter so as. to eliminate its iniiuence on thereceiver inputv circuit. Condenser 22' completed the alternatingcurrentcircuit at the receiving end-,of the transmission line by lay-passingresistors I8 and 20 and ammeter 2 I.

The transmitter The vdirect current potential difference impressedacross .terminals I3' and I5 at the transmitter is impressed across'thepoints 23 andv25,

a path of suitable resistance 26 of proper value being provided forheating the cathodey or lament 21 of the thermionic valve 28 which is ofthe audion type. The plate 29 of audion 28 receives direct currentpotential from p oint 23 connected to the mid point of an inductance3I,`

I the oscillating grid-lament circuit blocks out direct current ioWtherein and provides a path of low impedance for the oscillatinggrid-filament potential. The plate-cathode alternating lcurrent flowsthrough resistor 26, tap 30, tap 32 and plate 29, `and the grid-cathodealternating current ows through resistor 26, tap 30, tap 33, condenser34, tap 31 and grid 36, the platecathode alternating current andgrid-cathode alternating current both Aflowing through resistor 26. Inthe modication shown in Figure 2, the inductances 3l and 4I are inparallel, and a variable condenser 43 is connected across the terminalsof inductance 42 coupled to inductance 4 I. Adjustable condenser 44 isconnected in parallel with variable condenser ,43 and the Acombinedcapacitance eect of the condensers 44 and 43 can Ybe accurately anddelicately adjusted for calibration by'properly setting the condenser44.

It will be seen that when the oscillation set -up charges capacitor 34to maximum oscillating potential, the alternating grid-filamentcurrentof the audion 28 is at va maximum and the alternating plate-filamentcurrent also is at a maximum. As the 'charge on condenser '34 varies thealternating grid-filament and plate filament .currents .likewise vary,and the alternating potential acrossthe common current path 26 likewisechanges', and the alternating current potential across the points 23, 25isthe signalling potential impressed on the telephone transmission line.The plates of condenser 43 are adapted to be mechanically operated inany suitable manner by the pressure, liquid level, or other qualityto bemeasured to thereby vary its capacity. This variation in capacity4varies the frequency of the oscillations across terminals 23, 25.

The secondary transmitter circuit comprises condensers 43 and 44 andinductance 42, this circuit being shown inductively coupled to the`grid-filament andplate-filament circuits, but it will be understoodthat the secondary transmitof the coll ratios of inductances 42 Ato 4I.-As shown in Figure 2, the inductance 4I has a smaller number of turnsthan inductance 42, and therefore steps up the alternating potentialacross points 32, 33, to a higher value across .capacitor 43. Thispermits the use of a small lightv weight condenser 43 which is v erysensitive and accurate; 'I'he ground,45 of the transmitter is connectedthrough the wire 46 to the point 25 and serves as a common ground forthe receiver andtransmitter.

The receiver The oscillatingpotential across terminals I3 and I5' of thetransmitter is transmitted across the telephone lines to the receiverterminals I3 and I5, and with the switch 50 connected at 5I, thesignalling potential is impressed across capacitor 22 to the amplifieraudion 55. This audion which may be part of the receiver, preferably isof the indirectly heated type, the cathode 56 being heated by a filament51 connected in a suitable manner with a winding 'coupled to a Winding84 from which the heating current is obtained. The power supply terminalI2 provides a positive potential to anode 58 through wire 62, connectedat 6I with resistance 60, which in turn is connected to the terminal 59'of primary winding 59, the circuit being completed throughaudion 55,resistance 63 and wire I6 to the point I4. The cathode 56 thereiore isbiased positive with respect to ground an amount equal to the potentialdifference across the terminals 65 and 66 of resistance 63 and ispositive with respect to grid 54. Resistance 52 provides' a return pathfor the grid-filament direct current. The potential difference acrossthe terminals 65 and 66 preferably is selectedso that the gridpotential.. changes in grid 54 due to the oscillating signalpotentialprod'uce a'lineal change in the plate current. VCondenser 61 acts as .aby-pass capacitor providing a return path of I 12 and 13 respectively ofthe audions 14 and 15. With the receiver operating at optimumveciencythe grid-cathode circuits of audions 14 and 15 consume power which issupplied bythe plate circuit of amplifier tube 55. The 4transformerconsisting of windings 59, 10 and 1I has .a mutual inductance such thatthe impedance of the gridcathode circuits of audions 14 and 1521sreflected in the amplifier plate circuitV is equal at the vfrequencyrange at which the'transmitter-operates to the internal plateimpedanceof audion. 55.

Y low .reactance for the amplified alternating cur- Under theseconditions theamplifler Atube re-` quires a minimum signal potential toprovide the requiredV power for operating'the receiver. The audions 14and 15 are preferably' of the indirectly heated cathode type and areheated by current supplied from winding 85. The anodes 16 and 11 ofaudions 14v and 15 are connected to opposite sides of capacitor 80. vThecathodes 18 and 19 are biased at the correct positive potentialvrelative to the grids of their respective audicns by means of suitabledirect current sources of proper potential which may be batteries orrectiiiers of suitablecharacteristics. Such combined transformers andrectifiers shown at 68 and68 receiving their power from a suitablealternating current source.

The grid 12, which receives its potential from secondary winding 10, isexcited 180 out of phase with grid 13 which receives its potential fromsecondary winding 1I. Cathode 18 of audion 14 is connected to plate 11of audion 15 to maintain the potentials on cathode 18 and plate 11equal. When the grid 13 is positive with respect to the cathode 18 thecathode-plate current flows in audion 15 to charge capacitor 80.' On thenext half cycle when the grid 12 of audion 14 becomes positive and grid13 becomes negative the condenser 80 discharges through the plate 16 andcathode 18 of audion 14. During the charging cycle of capacitor 80 thecurrent flow through audion 15 passes through and is indicated onmilliammeter 82. The average pulsating charging current to capacitor 80as indicatedby milli ammeter 82 bears a definite relation to the fre.-quency of the signal current so that .changes in frequency of the signalcurrent caused by variationsvof condenser 43 at the transmitter areindicated by the meter 82. This meter 82 may be calibrated in suitableunits such as pounds pres sure, or' linear units to give a properindication of the quantity to be measured. I have found that, with agiven type of tube at 14 and 15 there is an optimum relation between thedirect current plate and grid voltages, and by suitable adjustmentof theplate potential across terminals I2 and I4 and of the grid-cathodepotentials at 68 and 68 the maximum current is obtained, at a givenfrequency, through 'the milliammeter 82 for a given input to thereceiver.

. Provision is made for testing the receiver. The

transformer 69 supplies an alternating current of known frequency andpredetermined potential to the terminals 86v and 81, and by connectingswitch 50 with 4terminal 81 and observing the reading of the indicatinginstrument 82 it can be determined whether the receiver is correctlyfunctioning.

In a telephone line as ordinarily connected and operated, the line isterminated in an impedance of a value equal to the characteristicimpedance of the line. However, in the present invention thetransmission line is terminated by inductance I9l and condenser 22'which complete the signal current circuit, and as there is no matchedterminal impedance the vline has a capacitive reactance.' impedance theattenuation of the transmission line, i. e., the line loss, is smaller.However, in this arrangement the transmission line circuit composed ofinductance I9, the transmission line and condenser 22 assumes a largephase angle. As is well known, a vacuumtube oscillator operates at thatfrequency for which the total phase angle of the circuits is zero.Since' the phase' angle of the circuit composed of resistance 26 andfilament 21, which circuit is in parallel with the transmissionlinecircuit, ordinarily is not zero, the primary oscillatory circuitcomposed of inductance 3| and the resultant capacitance of coupledinductance 4I must oscillate with an equal and opposite phase angle..

A change in the phase angle of the circuit including resistance 26 andfilament 21 therefore causes a corresponding change in frequency in .theprimary oscillatory circuit suchthat the total denser 22'.

By not using a matched terminal limit of the scale.

phase angle is restored to zero. The impedance of the transmission linewhich is determined byits length and other factors therefore aects thefrequency of the transmitter through its effect on the phase angle inthe circuit composed of resistance 26 and filament 21.

When the transmitter is calibrated at the fac; tory a simulatedtelephone line may or may not be connected between the terminals I 5, I5and I3, I3'. If no simulated line is used the only reactive impedanceshunting resistance 26 and filament 21' is inductance I9 in series withcon- This impedance is high so that under such conditions of calibrationthe phase angle in circuit 26, 21 is close to zero. Now, when theapparatus is installed in the eld and a telephone line is connectedacross terminals I5, I5 and I3, I3', or a simulated telephone line isused for calibration, the phase angle in circuit 26, 21 increases due tothe low impedance of the transmission line circuit so that the frequencyof the transmitter shifts from its calibrated point.

However, I found that if the inductance IS is set at a value such thatit is anti-resonated by the line within the range of frequency employed,the impedance of the resistance 26 is raised and the phase angle therebydecreased to a minimum. The nearer this phase angle is to zero thesmaller will be the effect on the frequency of the transmitter when adierent transmission line is used. Therefore the inductance I9 isadjusted and set in the factory at its anti-resonated value with asimulated line connected.

Direct current flows from filament 21, througn point 25, resistance 35and point 31 to,grid 36,

and its path is completed through the tube'. 'I'he potential betweengrid 36 and filament 21 is substantially that between points 31 and 25,so that when resistance 35 is varied the grid-filament potential ischanged. This in turn influences the plate-filament direct current.'I'he permeability of the iron core of inductance 3'I is determined bythe plate-filament direct current', flowing through inductance 3l, andchanges in this currentas produced by adjustment of resistance 35,consequently affect the inductance of Winding 3l and hence theoscillating frequency of the transmitter. 'I'he eect of adjustingresistance 35 on the direct current potential of grid is not critical,and this adjustment therefore can be used to adjust the' inductance ofwinding 3l Within certain limits.

In Calibrating the transmitter it; is connected to the receiver and thecondenser 43 is set at the zero limit of its movement and'resistance 35is adjusted until the receiver indicates zero. 'I'he adjustment ofcondenser 44 has a negligibleef, fect onthe frequency of the circuit atthe zero setting of condenser 43 because the capacity of condenser 44 isbutka small fraction of the capacity of condenser 43 at that setting.However, adjusmen't' of resistance 35 cannot correct the calibration ofthe transmitter at its high range because the resistance 26 has agreaterphase angle at the higher frequencies than at the lower frequencycorresponding to zero on the receiver scale. the highrange of the scalethe condenser 43 is set at the uppermost limit of its range of movementand condenser 44 is adjusted to the point at which the receiverindicates the uppermost This adjustment corrects for linear changes inthe phase angle of resistance Therefore, for calibration at 26 withchanges of frequency, and non linear 1| The operation of the apparatusvwill now be described. Direct current is supplied to points I2 and I4from the transformer I and full wave rectifier tube 1, the directcurrent taps being located at the points 6 and 8, and the inductances 9,II, and condensers 3 and I0 serving to smooth out the direct currentsupply. The transmitter A (Figure 2) is supplied with direct current atthe points I3 and |5' from the points I2 and I4 respectively at thepower supply, this direct current being transmitted to the transmitterover the same telephone lines which return the alternating currentpotential from the transmitter to the receiver. By observing the flow ofcurrent through the ammeter 2| and adjusting the resistance 20 to asuitable value, the

potential transmitted to the points I3' and I5' tion regulated power|00, this power being rectified by a vacuum tube can be adjusted to theproper value. The flow of current across the points 23 and 25 throughresistance 26 and filament 21 is utilized to heat the cathode 21 ofaudion 28.

The capacitor 44- is adjusted to a xed value when the instrument iscalibrated and remains unchanged during operation, and it will be seenthat changes in the capacity of condenser 43 which is actuated by anysuitable pressure responsive means or similar device controls theoscillating frequency of the transmiter as previously described. Y

The alternatingpotential is tapped at thel points 23, 25 in the commonplate-filament and grid-filament path and constitutes the alternatingsignal potential which is transmitted back over the telei phone line tothe points I3 and I5 at the receiver.

With theswitch connected at 5 I the oscillating signal potential passesthrough the condenser 22, which howeverdoes'not allow passage of thedirect current from the rectier tube 1, .to the amplier tube 55. 'I'heoscillating Apotential is am- 'pliiied in known manner by audion 55, andthe amplied oscillatory signal current is divided by the primaryinductance 59 and coupled sec'- ondary inductances 'I0 and 1I intotwocurrent paths 180 out of phase. The audions 14 and 15 have theircathode-anode interconnected respec-A tively, and the pulsatingcathode-anode direct current of audion 15 passing through condenser 80is transmitted through the milliammeter 82 In the modification shown inFigure 3, wherein like parts are designated bylikenumerals, the

transmitter is supplied with power from an intermediate point which maybe located any suitable distanceup to labout ten milesfrom thetransmitter. The receiver may be located at practically any distancefrom the point of application of the power supply. In this modificaissupplied to a transformer rectifier IOI and smoothed out by reactances|02, |03, andcondensers |04 and |05. The direct current potential is cutdown to a suitable value for the transmitter by adjustment of theresistance 20' as previously described, and inductance I9' prevents the`signal potential from being short circuited through capacitor |05.`vIntransmitter.

ductance I9', like inductance I9, can be used to compensate i'or theeffect of. the line on the frequency of the transmitter. The terminalsH3 and IIS of the power supply are located up to about ten miles fromthe transmitter and are connectedthereto over telephone lines, and the ibined resistance of the circuit shown in Figure 1 from the points I2 andI4 to and including the transmitter, and back again to the receiver.

In the modification shown in Figure 3 the constructionv and operation ofthe receiver is quite similar to that shown in Figure 1. In thisconstruction the direct current output of the full wave rectifier tube 1is not transmitted to the It serves "to energize amplifier audion andsupply current for charging condenser 80 in the same manner as in themodiiication shown in Figure 1. In order to permit the same receiver tobe used with either modification shownin Figures 1 and 3 and eliminateseparate calibration thereof, a resistance |20 is placed vacross theterminals I2 and I0. This'resistance lines and transmitter, and theleads back again to the points I2 and I4. The terminals |3 and I5 of thereceiver are connected to the points I3" and I5 of the power supply bytelephone lines. The direct current from the power supply is transmittedfrom the terminals II3 and H5 over telephone lines to the transmitter A(Figure 2) at the points I3' and I5 respectively, and the oscillatingpotential signal current is returned over the same telephone linesto thepoints |I3 and II5 at the power supply, from thence to the points I3 andI5 at the receiver, and as previously explained, produce the properreading on the miliammeter 82.

In the modied transmitter shown in Figure 4 the inductance 90 has moreturns than inductance 9|, and the point 23 is connected to the mid point9 2 of inductance 9|. 'I'he operation'of this transmitter is similar tothat shown in Figure 2, the elimination of inductance 3| providing amore simple construction.

In` the modiiication shown in Figure 5 a variable speed alternating-current generator comprising a pair of slip rings 94 and an armature isoperated by the quantity to be measured in any suitable manner. Power istransmitted through the telephone lines tothe terminals 95 and 96 andthence to the eld 91 .to excite the same. 'I'he generated lfrequencypasses through condenser 98 back to the transmission line, thiscondenser serving to block out' the direct current power 4supply and thechoke coil .91' blocking the gen- .condenser 43shown in Figure 2, likeparts of.

thisvtransmitter being correspondingly numbered.

It will be noted that the coupled inductances 4| and 42 are reversed inthis modication, and the reversal of these inductances produces amultiplied reactance eifect in the primary circuit. I use the termmultiplied reactance effect throughout the specication and claims todenote generically either a division or Vmultiplication of the reactanceelect, as division can be considered as an inverse multiplication.

In the modification shown in Figure 7, oscillating grid-filament andplate-filament currents are segregated and the potential drop caused bythe grid-filament current is utiliz'ed to impress an alternatingpotential on the transmission line. The direct current supply iscconnected across positive and negative terminals I 3 and I5respectively, and the positive potential is applied .to the plate 29through inductors 20| and 202 and returned lto the negative terminal I5'through the tube 28 and the lament 21. Condenser 34' blocks direct platepotential from the gridv circuit. The grid direct current flows throughinductances 202' and 203 and resistor 35 to iilament 21, it beingconfined to this path by condenser 201. current passes throughinductance 202, condenser 204, tothe lament 21, the inductance 20|conlining the current to this path. The oscillating grid-filamentcurrent passes through inductance 202', condenser 201 and resistor 26 tothe iilament 21, the inductances 203 and 20| confining the current tothis path. 'I'he alternating potential difference across resistance 26in the grid circuit is impressed on the terminals I3' and I5 to thetransmission line as the signal potential.

In the modication shown in Figure 8, theoscillating grid-filament andplate-filament currents are segregated and the potential drop caused bythe plate-filament current is utilized to impress an alternatingpotential on the transmission line. This arrangement gives the greaterrange of frequency change for a given capacity change, The directcurrent supply Vis connected across positive and negative terminals I3'and l5 respectively, and the positive potential is applied,

to the plate 29 through inductance 202, and returns to the negativeterminal I5 through the tube 28 and filament 21. The grid direct currentliows through inductance 202 and resistor 35 to filament 21. Theoscillating plate-filament current passes through inductance 202 andresistance 26 to the filament 21. I'he oscillating grid-lament currentpasses through inductance 202', and condenser 201 to the iilament 21.Condenser 34' blocks direct plate. potential from the grid circuit. Thealternating potential diierence across resistance 26 in the platecircuit is impressed on the terminals I3' and I5' to the transmissionline as the signal potential.

Figure 9 shows a modified transmitter employing a three wire system,'the signalling potential and the power supply being isolated at thetransmitter. In this modification the power is supplied to terminals I3and l5', and the oscillating signal output is tapped at the terminals I4'and' l5', the inductance I9 serving to 'isolate the signal potentialfrom the power supply, and the Capacitor 22 serving to isolate thesupply current from the signal output circuit. 'I'his system is usedwith a receiver and power supply like that shown in Figure 1 or 3, theinductance I9 and condenser 22 however being omitted as their equivalentis employed at the transmitter.

The invention may be embodied in other specific forms without departingfrom the spirit or 'Ihe oscillating plate-filamentessentialcharacteristics thereof. The present embodimentis therefore tov beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims ratherthan by the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein'.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a telemetric system, a transmitter including a vacuum tu'beoscillator for generating an oscillating signal potential, a directcurrent power supply, conductors for supplying direct current from saidpower supply to said oscillator. a reactance operated by the value to bemeasured for varying the frequency of the oscillating signal potential,a receiver including a frequency measuring device, said conductors beingconnected to the oscillating output circuit of said transmitter andtransmitting the oscillating signal potential to the receiver, acondenser at the receiver for isolating the supply current 'carried bysaid conductors from the receiver, and a relatively great inductance forisolating the signal potential from the power supply, said inductancebeing adjustable to compensate for the shift in phase angle of thetransmitter Idue to the impedance of the conductors.

2. In a telemetric system, a transmitter including a variableoscillation generator for producing an oscillating signal potential, adirect current power supply, conductors for supplying direct currentfrom said power supply' to said generator, a reactance operated by the'value to be measured for varying the frequency of the voscillatingsignal potential, a `receiver includconductors from the receiver, andmeans for isolating the signal potential from the power supply, saidlatter means being adjustable to compensate for the shift in phase angleof the transmitter due to the impedance of the conductors.

3. In a telemetric system, a transmitter including a vacuum tubeoscillator for producing anoscillating signal potential, means forsupplying current to said oscillator, a frequency measuring receiver,conductors for impressing the alternating signal potential on thereceiver, and an inductance effectively in shunt with the output circuitof said transmitter for compensating for the shift in phase angle at thetransmitter due to the imepedance of the conductors.

4. A transmitter including a vacuum tube oscillator, means for supplyingcurrent to said 'oscillator, means providing a common path for theplate-filament and grid-filamentoscllating currents, a transmissionline, and means for impressing the alterating potential developed acrosss aid common path upon said transmission line.

5. A transmitter including a vacuum tube oscillator, means for providingcurrent to said oscillator, means providing a common path for theplate-filament and grid-filament oscillating currents, means for varyingthe frequency of the alternating potential across s aid second namedmeans, a transmission line, and means for impressing the alternatingpotential developed across said second named means upon saidtransmission line. v

c. rn a transmitter including a vacuum tube oscillator, meanslor-*supplying direct current to said tron means in the path of theplate-nimmt cnrrent for dividing' the alternating potential difference,a portion of thealternating potential being utilized to tain oscillationci theoscillater, and the remainder of the potential being impressed onmid www conductors.

'z'. In a telemetric system, a transmitter includay tube oscilaltor, avoltage divider providing a common path for the plate-lilament', andgrid-nimmt oscillating current, means con nected across said voltagedivider for supplying power to the oscillator, a frequency measuringreceiver, and conductors connected across said voltage divider lor trathe oscillating across saldi voltage divider to the receiver.

8. A. transmitter including a vacuum tube orf cillatcr, means forsumming direct current to said oscillator, means providing a path forthe plate-filament and grid-filament oscillating currents, meansblocking direct current to the grid of said tube and providing a lowimpedance path for current to the grid, a transmission line, and meansfor the alternstng potential developed across said common path upon saidon line.

e. In a transmitter including a vacuum tube oscillator, a power supply,a means for supplying direct current from the power supply to saidoscillator, means providing a common path for the plate-moment andgridlament oscillating currents, for impressthe alternating potentialdeveloped'across said common path upon the transmimion line, and meansfor. isolating the alternating-current signal potential from the powersupply lo. In a telemetrlc system including a oscillator, a powersupply, conductors forA supplying direct current from the power supplyto said oscillator, providing a, common path for the plate-mantieni; andgrid-filament oscillating currents for producing an alternatingpotentialdierenoe, means for lmpreing the alternating potential ldcvelopcclacross said means upon said conductors, means for isolating the signalpotential from the conductors carrying direct current, means dependentupon a value to be for varying the frequency of the alternating signalpotential. a receiver lncluding a. frequency device for receiving thesignal potentialv from said conductors, and means for isolating thesupply ciment carrled by the conductors from the receiver.

11. A transmitter including a vacuum tube oscillator, means forsupplying current to the oscillator, means for dividing the supplyptential and utilizing a portion thereof for heating the moment of scidtube, said dividing means providing a common path for the plate-momentand grid-filament oscillating currents, means dependent on a value to bemeasured for varying the frequency of the alternating potentialacrosssaid common path, means for adjusting the grid potential toregulate the plate current at a predeteruuned value, means blockingdirectcurrent to the grid ci said tulle and providing a low impedancepath for current to the grid, a n and means for impressing thealternating potential developed across said common path upon saicltransmission line.

l2. A transmitter including a main oscillatory circuit havmg a vacuumtulle, for supplyng current to said circuit. a u i i Y l oscil Iatorycircuit coupled thereto to produce a mnltiplied reaclance elect therein,said secondary circuit a variable reactance, means to vary saidreactance to vary the frequency' or the circlnt, means pr a common pathlor the plate-filament and grida-lilament current, a on line, means un:Iimpressing the alternating potential developed across saidlcommon pathupon said line.

13. A transmitter including a vac tube oscillator, means for supplyingdirect current to said oscillator, means in the path of theplatefilament osdllating current for dividing the alternatingrliderence, a, secondary ancillatory circuit inductively coupled to thement circuit to produce a multiplied reactance eect trn conductors, aportion of the alternating potential in. the plate-t circuit being tooscillation of said oscillator, the remainder ol the alternatingpotential being on said transmission conductors.

14. In a telemetric system, a. inransmitter including a vacuum tubeoscillator, a voltage divider providing a common path for theplatefilament and gricl-iilament oscillating currents.,

means connected across said voltage divider for supplying power to theoscillator, means dependcnt on a value to be measured for changing thethereto to. produce a mnltiplied'reactance effect therein, saidsecondary circuit including a variable reactance adapted to be varied bya quantity tov be measured to vary the frequency of the potential in themain cir-` cuit., a frequency meter, and conductors for impressing thesignalling potential on the frequency meter.

16, In a. telemetric system, a transmitter including a main oscillatorycircuit having a vacnum tube, means for supplying current to saidcircuit, a secondary oscillatory circuit coupled thereto to produce a.multiplied reactance effect therein, said secondary circuit including a.variable reactance, means dependent on a quantity to be determined tovary said reactance to vary the frequency of the signalling potential inthe main oscillatory circuit, means for isolating the signal potentialfrom the power supply, .a frequency meter, and conductors for impressingtlie potential on the frequency meter.

EUSTACE G. WATIS.

